Quadrature detector and amplitude error correction method for quadrature detector
A method for correcting an amplitude error between an I signal and a Q signal which are outputted from a quadrature detector including a first multiplier for multiplying a reference signal and a measured signal, a first integrator for smoothing the output of the first multiplier to generate the I signal, a 90-degree phase shifter for generating an auxiliary reference signal from the reference signal, a second multiplier for multiplying the auxiliary reference signal and the measured signal, and a second integrator for smoothing the output of the second multiplier to generate the Q signal. The method includes the step of inputting the auxiliary reference signal, instead of the reference signal, to the first multiplier to obtain a first output signal and inputting the reference signal, instead of the auxiliary reference signal, to the second integrator to obtain a second output signal. Then a correction coefficient for amplitude error correction is calculated from at least one of a ratio between the Q signal and the first output signal and a ratio between the I signal and the second output signal.
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Claims
1. An amplitude error correction method for a quadrature detector which includes a first multiplier for multiplying a reference signal and a measured signal, a first integrator for smoothing an output of the first multiplier to produce an I signal and outputting the I signal, a phase shifter for generating an auxiliary reference signal having a predetermined first phase delay amount from the reference signal, a second multiplier for multiplying the auxiliary reference signal and the measured signal, and a second integrator for smoothing an output of the second multiplier to produce a Q signal and outputting the Q signal, characterized in that it comprises:
- a first step of measuring at least one of the Q signal and the I signal;
- a second step of varying the phases of the signals to be inputted to the first multiplier and the second multiplier so that a first output signal having an in-phase or reverse phase relationship to the Q signal is outputted from the first integrator and a second output signal having an in-phase or reverse phase relationship to the I signal is outputted from the second integrator; and
- a third step of calculating at least one of a ratio between the Q signal and the first output signal and a ratio between the I signal and the second output signal and determining the calculated ratio as a correction coefficient to be used for amplitude error correction.
2. The amplitude error correction method according to claim 1, wherein the first phase delay amount is 90 degrees.
3. The amplitude error correction method according to claim 1, wherein the second step is a step in which the auxiliary reference signal is inputted in place of the reference signal to the first multiplier so that the first output signal is outputted from the first integrator, and the reference signal is inputted in place of the auxiliary reference signal to the second multiplier so that the second output signal is outputted from the second integrator.
4. The amplitude error correction method according to claim 1, wherein the second step is a step in which a signal having a predetermined second phase delay amount from the measured signal is supplied in place of the measured signal to the first multiplier and the second multiplier so that the first output signal and the second output signal are outputted from the first integrator and the second integrator, respectively.
5. The amplitude error correction method according to claim 4, wherein both the predetermined first phase delay amount and the predetermined second phase delay amount are 90 degrees.
6. A quadrature detector which includes a first multiplier for multiplying a reference signal and a measured signal, a first integrator for smoothing an output of the first multiplier to produce an I signal and outputting the I signal, a phase shifter for generating an auxiliary reference signal having a predetermined phase delay amount from the reference signal, a second multiplier for multiplying the auxiliary reference signal and the measured signal, and a second integrator for smoothing an output of the second multiplier to produce a Q signal and outputting the Q signal, characterized in that it comprises:
- phase switching means for switching the phases of the signals to be inputted to the first multiplier and second multiplier so that a first output signal having an in-phase or reverse phase relationship to the Q signal is outputted from the first integrator and a second output signal having an in-phase or reverse phase relationship to the I signal is outputted from the second integrator.
7. The quadrature detector according to claim 6, wherein the predetermined phase delay amount is 90 degrees.
8. A quadrature detector which includes a first multiplier for multiplying a reference signal and a measured signal, a first integrator for smoothing an output of the first multiplier to produce an I signal and outputting the I signal, a phase shifter for generating an auxiliary reference signal having a predetermined phase delay amount from the reference signal, a second multiplier for multiplying the auxiliary reference signal and the measured signal, and a second integrator for smoothing an output of the second multiplier to produce a Q signal and outputting the Q signal, characterized in that it comprises:
- a switch operable, when switched, for inputting the auxiliary reference signal in place of the reference signal to the first multiplier and inputting the reference signal in place of the auxiliary reference signal to the second multiplier.
9. The quadrature detector according to claim 8, wherein the predetermined phase delay amount is 90 degrees.
10. A quadrature detector which includes a first multiplier for multiplying a reference signal and a measured signal, a first integrator for smoothing an output of the first multiplier to produce an I signal and outputting the I signal, a first phase shifter for generating an auxiliary reference signal having a first phase delay amount from the reference signal, a second multiplier for multiplying the auxiliary reference signal and the measured signal, and a second integrator for smoothing an output of the second multiplier to produce a Q signal and outputting the Q signal, characterized in that it comprises:
- a second phase shifter for providing a second phase delay amount to the measured signal; and
- a switch operable, when switched, for inputting an output signal of the second phase shifter in place of the measured signal to the first multiplier and the second multiplier.
11. The quadrature detector according to claim 10, wherein both the first phase delay amount and the second phase delay amount are 90 degrees.
Type: Grant
Filed: Nov 15, 1996
Date of Patent: Jul 28, 1998
Assignee: Advantest Corporation (Tokyo)
Inventor: Takashi Shimura (Tokyo)
Primary Examiner: Don N. Vo
Assistant Examiner: Amanda T. Le
Law Firm: Oblon, Spivak, McClelland, Maier & Neustadt, P.C.
Application Number: 8/751,159
International Classification: G06F 744;
